Trim fat from meat. If necessary, cut meat to fit into 3.5 - 4 quart slow cooker. Place meat in cooker; sprinkle with parika. Sprinkle lightly with salt and ground black pepper. Top with chile pepper and onion. Add broth and vinegar.
Cover and cook on low for 10-12 hours or on high for 5-6 hours. Transfer meat to serving platter, reserving juices. Cover meat and keep warm.
For sauce: Skim off fat from juices. Measure 1 cup juices. In small bowl, combine sour cream and arrowroot. Slowly whisk in juices; return to slow cooker. If using low setting, turn slow cooker to high. Cover and cook about 15 minutes more or until sauce is thickened.
Thinly slice meat across the grain. Serve meat with sauce.